13. Balance welding on each side of the neutral axis, i.e. do not weld all one side before starting the other.

14. Weld fabrications clamped back to back and preset if possible; alternatively stress relieve before releasing from the clamps.

15. Use block welding to prevent movement.

16. When block welding thick plate, butter the sides of the preparation and build up the buttering progressively towards the center of the joint, so that most of the joint can contract transversely before the joint is bridged.

17. Weld first the joints that cause the most contraction.

18. Make use of sub-assemblies.

19. Make frequent dimensional checks during welding, and if distortion is evident change the welding sequence or the clamping arrangements accordingly.

The welding procedure adopted does not actually matter for distortion control in structural welding.The shape of the structure and the heat input involved during welding is what causes distortion. For example, if built up sections with thickness greater than 16 mm with lengths varying from 5M to 10M are to be welded it is always advisable to use GMAW/FCAW or SAW for both Quality and production. But these being high heat input processes and the nature of welds being straight lengthy beads, it is advisable that the sections be placed on LEVEL PLATFORMS, FIT UP BE CHECKED FOR STRAIGHTNESS,WARPS IN PARENT METALS CAUSED BY GAS CUTTING. These checks are a must.Thereafter one could clamp down the sides to be welded to the platform and a staggered sequence of welding from both sides involving 2 to 4 welders(depending on the weld length) may be adopted. 2 welders from opposite ends on opposite sides may start welding simultaneously and weld progression may be towards center or start from center and proceed towards ends.Alternately staggered weld areas may be marked on opposite sides and welders may weld alternate staggered areas on their own sides but from opposite ends. The idea is to achieve EVEN HEAT DISTRIBUTION. AFTER WELDING, CLAMPS SHALL NOT BE REMOVED TILL THE WELDED AREAS HAVE COOLED TO AMBIENT. In case of rolled sections like trestles, purlins etc. where continuous welding is not involved SMAW can be safely used.Electrode dia should not be allowed to exceed 3.15mm. This is a general overview. If some details of structure type is known I can be more specific.

On Thu, 11 Aug 2011 15:25:03 +0530 wrote

> Dear friends,

By adopting which welding procedure (SMAW/GMAW/FCAW) we can reduce distortion in structural welding

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